Closure for microwave oven



Dec. 16, 1969 E. M. TINGLEY 3,484,573

CLOSURE FOR MICROWAVE OVEN Filed Aug. 8, 1968 2 Sheets-Sheet l fw l 2% www@ @fm Dec. 16, 1969 E. M. TINGLEY' 3,484,573

CLOSURE FOR MICROWAVE OVEN Filed Aug. 8, 1968 2 Sheets-Sheet 2 United States Patent O 3,484,573 CLOSURE FOR MICROWAVE OVEN Egbert M. Tingley, Kankakee, Ill., assignor to Geo. D. Roper Corporation, Kankakee, Ill., a corporation of Delaware Filed Aug. 8, 1968, Ser. No. 751,283 Int. Cl. Hb 9/06 U.S. Cl. 219-10.55 12 Claims ABSTRACT OF THE DISCLOSURE A closure for microwave oven in the form of a continuous exible metal sheet perforated overall and mounted for movement to an out of the way position as in a roll top desk with means for sealing the edges against escape of microwave energy. Rigidification is provided by transversely extending, guided reinforcing bars.

It is an object of the present invention to provide a closure for a microwave oven which is uniquely suited to such an oven and which constitutes a substantial departure from the doors used on ovens of conventional design, More specifically, it is an object to provide a closure which provides an efficient barrier to the passage of microwaves, which avoids thick or insulated sections, which permits air circulation combined with viewability of the entire oven contents even in closed position, and which is easily opened and closed with only fingertip pressure. It is a more specific object to provide a closure which is formed of thin exible metal but which is nevertheless inherently durable and long lived. It is yet another object to provide a closure which is exceedingly light and compact, avoiding thick or insulated sections, which is inherently inexpensive an usable for microwave ovens which are either permanently installed or capable of portable or semi-portable use.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

FIGURE 1 is a perspective view of a microwave oven employing the present invention;

FIG. 2 is a fragmentary vertical section taken through the oven of FIG. l;

FIG. 3 is a fragmentary front view of the four corners of the closure;

FIG. 4 is a fragmentary section looking along the line 4-4 in FIG. 3;

FIG. 5 is a fragmentary section taken through one of the reinforcing bars and looking along the line 5-5 in FIG. 4;

FIG. 6 is a fragmentary section through the top seal looking along line 6 6 in FIG. 3;

FIG. 7 is a similar section through the bottom seal looking along line 7-7 in FIG. 3; and

FIG. 8 is a composite fragmentary perspective of the upper and lower left-hand corners of the structure.

While the invention has been described in connection with a preferred embodiment, it will be understood that the invention is not limited to the particular embodiment shown and that it is intended, on the contrary, to cover the various alternative and equivalent forms of the invention included within the spirit and scope of the appended claims.

Turning now to FIGURE 1 there is shown a microwave oven 10 having a metal housing which includes end surfaces 11 and 12, a top surface 13, a back surface 14 and a front surface 15. Arranged along the lower edge of the front surface is a control panel 16. The surfaces together define a shielded cavity 17. Means (not shown) are provided for setting up a high intensity microwave field with- ICC in the cavity which is constantly varied in mode by a stirring device or the like well known to those skilled in the art.

Formed in the front surface is an opening 20 having lzalteral edges 21, 22, a lower edge 23 and an upper edge In accordance with the present invention a closure is provided for the cavity opening which includes a sheet of thin flexible metal having a pattern of closely spaced perforations and confined along the edges in tracks which not only hold the closure in its active shielding position but which extend upwardly and rearwardly into a storage space above the oven housing. Each of the tracks consists of two closely spaced flat strips which overlappingly and confiningly engage the edges of the sheet and which provide good mechanical and electrical contact to prevent escape of microwave energy. Thus, turning to the drawing, a metal sheet 30 is provided formed of non-corrosive metal such as stainless steel and of a thickness which may range, say, between 0.005 to 0.020 inch. The sheet has lateral edges 31 and 32, lower edge 33 and an upper edge 34 and the sheet is, moreover formed with an all-over pattern of vperforations 35 which are of small dimension compared to the microwave length, say 0.10 inch or less and which may occupy approximately half of the total area. For the purpose of maintaining a good electrical connection between the metal housing and the closure sheet, while permitting easy friction sliding movement of the sheet between its active and stored positions, a track 40 is provided at the left hand side which consists of a pair of metal strips 41, 42 defining a space 43 between them and which are secured to the oven structure by means of metal screws 4S, or the like. Along the opposite edge a similar track 50 is provided made up of at strips 51, 52 secured by screws 55. The inner strip on each side, indicated at 42, 52 is preferably formed of thin flexible metal biased relatively inwardly against the confined edge of the sheet. The continuous electrical contact, combined with the overlapping, provides a joint which efficiently seals against the loss of microwave energy. The upper and lower edges 33, 34 are preferably dimensioned and positioned so as to snugly overlap the lower and upper edges 23, 24 of the cavity opening'.

For the purpose of insuring a continuous metallic seal at the lower edge of the door, an auxiliary sealing member 55 is provided secured to the lower edge 23 of the opening and which is made of springy metal of good conducting properties. The member 55 preferably has a rounded front surface and an initial set which causes it to be biased outwardly against the lower edge of the door when the latter is in closed position. If desired, the member may be slotted to provide individual contacting fingers as is well known in this art. At the upper edge 24 of the opening, a simple form of labyrinth or choke is employed to prevent the escape of microwave energy. To this end a sealing bar 56 is provided along the upper edge of the opening, the upper edge of which is overlappingly engaged by an inverted U-shaped member 57 formed along the upper edge of the door. If ldesired, the member 57 may be made integral with the metal sheet 30, forming the door proper, as shown. The choking effect provided by the overlap insures a leakproof joint even though light contact pressures are employed, thus insuring that the door remains easily movable with applica tion of only fingertip pressure.

In accordance with one of the primary features of the present invention, a series of horizontal reinforcing bars 60 are provided which are secured to the surface of the sheet 30, preferably by spot welding. Such bars are all the same length and have ends 61, `62. Taking the bar 60 shown in FIG. 4, by way of example, a relief is provided in the form of a notch 63 for receiving and accommodating the strip 41 which forms a portion of the track so that the bar overlaps the track.

For the purpose of confining the bars 60 against endwise movement and against movement perpendicular to the plane of the sheet, bar-retaining track members 71, 72 are provided. Taking the member 71 by way of example, it will be seen that it is of Z cross section having a mounting leg 73, an upstanding leg 74, and a parallel leg 75. The leg 74 serves to prevent endwise movement of the bar 60, and hence of the sheet 30, while the leg 75 which overlies the ends of the lbars 60, prevents any inward or outward movement of the bars relative to the plane of sheet. The net effect is to guide the sheet smoothly while keeping it in a centered position with respect to the tracks in which it is received, minimizing wear and the possibility of damage due to rough usage. A stop 76 for the lowermost bar defines the limit of closure movement.

In accordance with one of the aspects of the invention, the confining -frictional contact between the strips 41, 42, and the edge of the sheet is terminated at a level above the upper edge 24 of the opening so that the frictional loading is relieved as the closure is moved into its upper, storage position. Such frictional unloading is achieved in the present instance by causing the strips 41, 42 to diverge as indicated at 80, the strip 41 continuing upwardly and rearwardly at an angle within the storage space 81 and the companion strip 42 being secured, in horizontal position, on the top surface 13 of the housing. A stop 82 limits the movement of the closure in the upward and rearward direction. The bar retaining track members 71, 72 are preferably terminated, as indicated at 83, in the region of the upper edge 24 of the opening in order to further relieve the frictional loading upon the closure. Because of the fact that the front surface of the housing is sloped with respect to the vertical and 'because of the fact that the storage position is sloped with respect to the horizontal, in the space 81, bending of the sheet is limited ot an angle on the order of 45 so that binding in the region of the bend is completely avoided. As a result, the closure may be raised and lowered by light fingertip pressure, either applied to a handle 85 or applied to the lower one of the reinforcing bars 60.

While the storage position of the closure is visible in FIG. l, it will be understood that a decorative outer shell or cover 85 may be provided if desired, occupying the position shown by the dotted outline in FIGS. l and 2, the mounting of such an outer shell being a matter well within the skill of the art.

The closure described above has been found to be uniquely suited to a microwave oven. There is no necessity, in such an oven, to use the thick, insulating sections which are employed in ovens of the conventional type. On the contrary, it is desirable to have a free flow of air through the openings or perforations in the sheet for escape of moisture. The same perforations, occupying approximately half of the total area, make the sheet 30 effectively transparent so that the entire interior of the oven maybe viewed, with illumination provided by a suitable lamp 90, even when the closure is lowered into closed position. This is to be contrasted with conventional closures in which normally only a small or central portion of the total area is available for viewing. Because of the good contact and overlap of the conducting members about the periphery of the sheet 30, usually referred to in the art as weather stripping effect all of the microwave energy is effectively sealed inside the cavity insuring high utilization of the energy and avoiding such problems as radio and TV interference or a possible hazard to the user. Since the structure is so light and compact, the closure is not only suited for stationary microwave ovens lbut is ideal for those of a portable or semi-portable nature.

While certain of the claims recite that the track at each side is made up of two flat conducting strips, it will be understood that, if desired, one of the strips may be integral with the metallic front face of the housing. Also, while it is preferred to have the closure slide vertically, with storage in the upper position, it will be apparent that the directions upper, lower, and the like are to be considered as relative only. Stated in other words, the oven shown need not be oriented as in the drawing but may be mounted on one of its end panels, or even inverted, without affecting the readability of the claims.

I claim as my invention:

1. In a microwave oven having a rectangular cavity opening defined by upper and lower edges and a pair of lateral edges, a closure comprising, in combination, a sheet of thin flexible metal having a pattern of closely spaced perforations, a track along each of the lateral edges, each track being formed of two closely spaced fiat strips of conductive metal between which a lateral edge of the sheet is received, a series of horizontal bars secured to the surface of the sheet and spaced in parallel relation, at least one of the strips being tiexible and biased inwardly toward the sheet to hold the edge of the sheet snugly yet freely slidable and the sheet 'being positioned and dimensioned to closely overlie the upper and lower edges of the cavity when in closed position to prevent escape of microwave radiation.

2. In a microwave oven having a rectangular cavity opening defined by upper and lower edges and a pair of later edges, a closure comprising, in combination, a sheet of flexible metal having a pattern of closely spaced perforations, a track along each of the lateral edges and extending upwardly beyond the opening, each track being formed of two closely spaced iiat strips of conductive metal between which a lateral edge of the sheet is received, at least one of the strips being flexible and inwardly biased to hold the edge of the sheet snugly yet freely slidable and the sheet being positioned and dimensioned to closely overlie the upper and lower edges of the cavity when in closed position to prevent escape of microwave radiation, a series of horizontal bars of equal length secured to the surface of the sheet and spaced in parallel relation, and means abutting the ends of the bars for guiding said bars for upward and downward movement while maintaining the sheet in a central position with respect to the tracks.

3. In a microwave oven having a rectangular cavity opening defined by upper and lower edges and a pair of lateral edges, a closure comprising in combination a sheet of thin fiexible metal having a pattern of closely spaced perforations, a track along each of the lateral edges and extending upwardly beyond the opening, cach track being formed of two closely spaced flat strips of conductive metal between which a lateral edge of the sheet is received so as to be in substantially continuous electric contact with said tracks to prevent escape of microwave radiation, a series of horizontal bars of equal length secured to the surface of the sheet in spaced parallel relation, each of said bars being relieved at its ends to provide a space between the end of the bar and the sheet for accommodation of one of the strips.

4. The combination as claimed in claim 3 including a bar retaining track member engaging the bars at their respective ends for guiding the bars in their vertical movement while preventing any movement of the bars perpendicular to the plane of the sheet.

5. The combination as claimed in claim 3 in which the relief at the ends of the bars is provided by notching the bars and in which the bar retaining track is of Z configuration.

6. In a microwave oven having a rectangular cavity opening defined by upper and lower edges and a pair of lateral edges with a storage space above the upper edge, a closure comprising, in combination, a sheet of thin flexible metal having a pattern of closely spaced perforations, a track along each of the lateral edges and extending upwardly beyond the opening and into said storage space, each track being formed of two closely spaced flat strips of conductive metal between which a lateral edge of the sheet is received, a series of horizontal bars Secured to the surface of the sheet in spaced parallel relation, bar retaining track members for engaging the respective ends of the bars and for -conning the bars against movement perpendicular to the sheet, at least one of the strips of each track being flexible and inwardly biased for light frictional engagement with the edge of the sheet thereby to provide continuous electrical contact therewith to prevent escape of microwave radiation from the cavity, the contact between one of said strips and the edge of the sheet terminating at a level above the upper edge of the cavity so that the sheet is frictionally unloaded as it is moved upwardly into the storage space.

7. The combination as claimed in claim 6 in which the strips forming the track diverge from one another at a level above the level of the upper edge of the cavity.

8. The combination as claimed in claim 6 in which the bar retaining track member terminates in the region of the upper edge of the cavity and in which the strips forming the track for the sheet are bent to provide a rearwardly extending path for the sheet leading to the storage space.

9. In a microwave oven the combination comprising a housing having a cavity and front surface provided with a rectangular cavity opening dened byupper and lower edged and a pair of lateral edges, as well as a storage space above the housing, a sheet of thin flexible metal having a pattern of closely spaced perforations, a track along each of the lateral edges having an active portion and extending rearwardly and upwardly into the storage space to deline a storage space portion, each of said tracks being formed of two closely spaced at strips of conductive metal between which a lateral edge of the sheet is received, a series of horizontal bars secured to the surface of the sheet in spaced parallel relation, said strips holding the edges of the sheet in frictional conductive engagement to prevent escape of microwave radiation, the active portion of the track being sloped with respect to the vertical and the storage portion of the track being sloped with respect to the horizontal to minimize the angle of bend of the sheet as it is moved from active position to storage position.

10. In a microwave oven having a rectangular cavity opening delined by upper and lower edges and a pair of lateral edges, a closure comprising, in combination, a sheet of flexible metal having a pattern of closely spaced perforations, a track along each of the lateral edges and extending upwardly beyond the opening, each track being formed of closely spaced conducting surfaces between which a lateral edge of the sheet is received so as to be in substantiall ycontinuous electric contact with said tracks, the upper edge of the sheet having a channel of inverted U-shaped cross section, a sealing bar of conductive metal extending along the upper edge of the opening in the path of movement of the U-shaped portion for entering therein when the door is in its closed position to prevent the escape of microwave radiation, and a series of horizontal bars of equal length secured to the surface of the sheet and spaced in parallel relation.

11. In a microwave oven having a rectangular cavity opening defined by pairs of parallel edges, a closure comprising, in combination, a sheet of thin metal dimensioned to extend beyond the edges, tracks along one pair of edges and extending beyond the opening, each track being formed of two closely spaced faces of conductive metal between which an edge of the sheet is overlappingly received so as to be in substantially continuous electric contact with said tracks, a series of panel reinforcing bars secured to the surface of the sheet and in spaced parallel relation perpendicular to the tracks for moving the sheet along the tracks between closed and open positions, and means at the ends of the sheet for sealing the sheet with respect to the remaining pair of edges when the sheet is in closed position to prevent escape of microwave radiation.

12. In a microwave oven having a metallic housing defining a cavity and having a rectangular opening de ned by pairs of parallel edges, a closure comprising, in combination, a sheet of thin metal dimensioned to extend beyond the edges, stationary track members respectively arranged along one pair of edges and extending beyond the opening, each track member having conductive sealing means associated therewith intimately coupled to the sheet so as to be in substantially continuous electric contact with said tracks to prevent escape of `microwave radiation when the sheet is in closed position while permitting relative movement of the sheet to open position, a series of panel reinforcing bars secured to the surface of the sheet and in `spaced parallel relation perpendicular to the track members for moving the sheet along the track members between the closed and open positions, and means for sealing the end portions of the sheet with respect to the remaining pair of edges to prevent escape of microwave radiation when the sheet is in closed position.

References Cited UNITED STATES PATENTS 2,140,836 12/1938 Gerhardt 312-297 X 3,177,334 4/1965 Kinkle 219--l0.55 3,297,377 1/1967 Smith 312-297 X 3,304,401 2/1967 Long 219-10.5S

JOSEPH V. TRUHE, Primary Examiner L. H. BENDER, Assistant Examiner U.S. C1. X.R. 312-297 

